testing: print cpu type as label for benchmarks

Supports 386 and amd64 architectures on all operating systems.

Example output:
$ go test -bench=.*
goos: darwin
goarch: amd64
pkg: strconv
cpu: Intel(R) Core(TM) i7-3520M CPU @ 2.90GHz
BenchmarkAtof64Decimal-4        	24431032	        46.8 ns/op
...

As the displayed CPU information is only used for information
purposes it is lazily initialized when needed using the new
internal/sysinfo package.

This allows internal/cpu to stay without dependencies and avoid
initialization costs when the CPU information is not needed as
the new code to query the CPU name in internal/cpu can be
dead code eliminated if not used.

Fixes #39214

Change-Id: I77ae5c5d2fed6b28fa78dd45075f9f0a6a7f1bfd
Reviewed-on: https://go-review.googlesource.com/c/go/+/263804
Trust: Martin Möhrmann <moehrmann@google.com>
Reviewed-by: Keith Randall <khr@golang.org>

1 files changed, 31 insertions, 0 deletions

diff --git a/src/internal/sysinfo/sysinfo.go b/src/internal/sysinfo/sysinfo.go
new file mode 100644
index 0000000000..961be7abae
--- /dev/null
+++ b/src/internal/sysinfo/sysinfo.go
@@ -0,0 +1,31 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package sysinfo implements high level hardware information gathering
+// that can be used for debugging or information purposes.
+package sysinfo
+
+import (
+	internalcpu "internal/cpu"
+	"sync"
+)
+
+type cpuInfo struct {
+	once sync.Once
+	name string
+}
+
+var CPU cpuInfo
+
+func (cpu *cpuInfo) Name() string {
+	cpu.once.Do(func() {
+		// Try to get the information from internal/cpu.
+		if name := internalcpu.Name(); name != "" {
+			cpu.name = name
+			return
+		}
+		// TODO(martisch): use /proc/cpuinfo and /sys/devices/system/cpu/ on Linux as fallback.
+	})
+	return cpu.name
+}